Brake control apparatus



April 14, 1942- E. E. HEW|TT BRAKE CONTROL APPARATUS M MM UZEZYW 1 w25mm. 11V, w

m2 Nm m9 QS E E upm' ATTORNEY Patented Apr. 14, 1942 UNlTED STATESPATENT @FMCE 2,279,398 BRAKE CONTROLAPPARATUS Ellis E.Hewitt,'Edgewo`od, Pa., assignor to The Westinghouse Air Brake Company,Wilmerding, Pa., a corporation of Pennsylvania Application october 31,1940, serial No. 363,591 (c1. 30s- 21) 9 Claims.

This invention relates to brake control apparatus for preventing slidingof vehicle wheels and has particular relation to brake control apparatusincluding means automatically responsive to the slipping of vehiclewheels for initiating a rapid release of the brakes associated withV thewheels to prevent the sliding thereof.

As is well known, if the braking force applied to a vehicle wheel issuch as to exceed the limit A decelerating to the locked condition andsliding.

It should be understood that the terms slide and slip or slidingcondition and slipping condition as applied to a vehicle wheel hereinare not synonymous, a slidingwheel being one that is dragged along therail in a locked or nonrotative condition while a slipping wheel is onewhich is rotating at a speed less thana Ispeed corresponding to vehiclespeed at a given instant.

In Patent No. 2,140,620 of Clyde C. Farmer, a

vehicle wheel brake control apparatus is disclosed'including a rotaryinertia device responsive to the rotative deceleration of a vehiclewheel at a slipping rate for initiating a rapid release of the brakesassociated with the slipping wheel so as to prevent the sliding thereof.At the same time, the apparatus is automatically` conditioned inresponse to the initiation of slipping of the Wheel to limit the degreeof reapplication of the brakes on the slipping wheel to a lesser degreethan that which initiated the slipping so as to prevent possiblerecurrence of slipping. Reapplication of the brakes on a wheel whichslipped is effected automatically as the wheel accelerates back towardvehicle speed.

It is an object of my present invention to provide a brake controlapparatus of the type disclosed in the above mentioned Patent 2,140,-620 and characterized by a novel arrangement whereby the degree ofreapplication of the brakes on a Wheel which slipped is not limited to alesser value than that which initiated the slipping of the wheel unlessa predetermined time elapses following the instant the wheel firstbegins to slip during any one application.

It is a further object of my invention to provide brake controlapparatus of the character indicated in the foregoing object wherein arapid reduction of the degree of application of the brakes associatedwith a given wheel is initiated at the time the wheel begins to slipeffective also, at the same time, to cause sanding o f the rails inadvance of the slipping wheel and other wheels of the vehicle. A

It is a further object of my invention to provide a brake controlapparatus of the character gli Cil

indicated in the foregoing objects and further characterized by timingmeans utilizing the time A required for the pressure in a sandingreservoir to reduce to below a certain pressure for determining thedegree of reapplication of the brakes on the slipping wheel with respectto the degree of application in effect at the time the wheel first beganto slip.

,The above objects and other objects of my invention which will be madeapparent hereinafter, are attained bylmeans of an illustrativeembodiment of my invention shown in the single figure of theaccompanying drawing. y

Description of equipment Referring to the single figure of the drawing,the apparatus Ais shown in connection with a single four-wheel truck,only one wheel II for each aXle or wheel unit of the truck being shown.

For simplicity, the brake shoes associated with the wheels II are notshown. They may be of the conventional clasp type engaging the rim ofthe wheel and applied and released through conventional brake riggingVin response tothe supply of fluid underpressure to and the release ofuid under pressurefrom a brake cylinder I2.

The apparatus whereby the operator ofthe car or train controls thesupply of fluid under pressure to and the release of fluid under pres'-sure from the brake cylinder I2 may be any desired type, either of theso-called automatic or straight-air type. I have shown a simplified formof straight-air brake control apparatus including two train pipes I4 andI5 hereinafter respectively designated the control pipe and the supplypipe, a reservoir IB towhich the supply pipe I5 is constantly connected,and a manual-v ly operated self-lapping brake valve I1. The fluidpressure brake control apparatus further includes, according to myinvention, a so-called reapplication control valve mechanism I8 and adifferential relay valve mechanism I9, both of which will be presentlydescribed in detail.

Connected to the control pipe Ill by a branch pipe I4a and operativelyresponsive to variations of fluid pressure in the control pipe I4, is asocalled pressure switch 2|. Pressure switch 2| may be of any well-knowntype, preferably snapv acting, adapted to cause its movable contactmember 22 to be `snapped into its closedV position engaging a pair ofinsulated fixed contacts 23 in response to the increase of pressure inthe control pipe III above a certain low pressure such as five poundsper square inch. Conversely, when the pressure in the control pipe I4reduces below ve pounds per square inch, the contact 22 of CII thepressure switch 2| is snapped to its open .Y

position outof engagement with the fixed contacts 23.

The sanding apparatus comprises a pair of sanding devices 25-of theusual type adapted to cause the deposition of sand'in advance` of thevehicle wheels upon the supply of fluid under pressure thereto and tocease depositing sand xed contacts 23when the pressure in the reser-Vvoir l26 reduces below a pressure suchas iive pounds per square inch,and snappedv toits open position disengaging the contacts 23 wheneverthe pressure in the reservoir 26 exceeds fiveV pounds per square inch. s

Associated with the pressure switch 28 is a conventional. relay 29having a single contact which is shifted to itspicked-up` or closedposition in response to energization of the magnet winding thereof andrestored to its dropped-out or open position when the magnet winding isdeenergized.

In addition, the apparatus includes a wheelslipeiesponsive device 3| `ofthe rotary inertia type which may be associated with each of the wheelunits as by mounting at the end of the usual axlejournal in the mannerdisclosed and claimed in' Patent 2,198,033 of Clyde C. Farmer. Thewheel-slip-responsive devices 3| are not in themselves my invention andthus a complete description` thereof isr deemed unnecessary herein sincereference may be had to the abovementioned Farmer patent for details ofconstruction and mounting thereof. It issuicient to say for purposes ofthe present invention that the wheel-slip-responsive devices 3| includeva switch device Bla which is operated to closed position whenever. andas long as the rate of rotative deceleration or acceleration of thevehicle wheels with which it is associated exceeds a' certain rate suchas ten miles per hour per second; Inview of the fact that a rate of tenmiles per hour per second decelerationy and acceleration isnot attainedby the vehicle wheels unless theyare slipping, it will be understoodthat the switch devices 3`Ia ofV the wheel-slipresponsive devices 31|are not operated to closed position during the normal rate ofdeceleration and acceleration' of thel vehicle wheels.

The wheel-slip-responsive devices 3| are ef.- fective, in a mannersubsequently to be described, to control the operation of thereapplication control valve mechanism I8 and the differential relayvalve mechanism I9.

Considering the parts of the equipment in greater detail, theself-lapping brake valve I1 is of the type described and claimed inPatent V2,042,112 of Ewing K. Lynn and Rankin J Bush and accordinglyonly a functional description thereof is given herein. The brake valve|1 has an operating handle |1av which is shiftable in a horizontal planefrom a normal brake release position into an application zone. Brakevalve `handle |1a operates a rotary operating shaft brake valve handleI1a is shifted into its application zone, uid under pressure is suppliedfrom the reservoir I6 tothe control pipe I4.

u Theconstruction of thebrake valve I1 is such that* whenv the. pressurein the control pipe reaches a value corresponding to the displacement ofthe brake valve handle out of its brake release position, the supply tothe pipe I4- is automatically lapped'or cut-off. Thus the pressureestablished by the brake valve inthe control pipe I 4 is substantiallyproportionate to the degree of displacement of the brake valve handle`|1a out of its brake-release position.

If the pressure in the control. pipe I4 tends to reduce due to leakageor other causes, the brake valve` |1 operates automatically to supplyuid under pressure thereto to maintain a pressure thereinv correspondingto the position ofthe brake valve handle |1a. This pressure-maintainingfeature of the brake valve I1 will be referred to hereinafter inconnection with the reapplicationof the brakes on a slipping wheel.

The reapplication control valve mechanism I8 comprises a suitable casing35 having formed therein a bore 36 inV which a piston 31 operates. Acover 38=having a bore 36 conforming `to the bore 36 in the casingV 35-and providing an ex- `tension thereof is` secured to the casing 35 insealed relation as by a gasket 39T and. suitable` screws orbolts, notshown.

The piston 31 is providedv with a stemy 4| that extendsdownwardlythrough a passage 42 into engagement with the upper surface ofa piston valve 43 that operatesin another bore 44'formed inthe casing35.

Secured `to the casing` 35 as by a suitable gasketv45 and suitablescrews or bolts, not shown, 1s a cover plate 46 which closes the openend of the bore A44. Interposed between the cover 46 and the lower faceof the piston valve 43 is a coil spring 41 which urges the piston valveupwardly into seated relation on an annular rib seat 48 surrounding theopening of the passage 42 at the base of the bore 44. A suitable annulargasket .49 is provided in the upper face of the plston valve 43- vforVengaging the rib seat 48 in sealing relation.

The stem 4I of the piston 31 is of such length that when thefpistonvalve-43 is seated on the rib seat 48, the piston 31 is raised to anunseated position with respect to an annular rib seat 5I surroundingtheupper opening of the passage 42 at the base of the bore 36. Aprojecting lug or finger 53 formedon the inner surface of the cover38extends downwardly into the bore 36 and limits the upward movement ofthe piston 31.

An annular gasket 54 is provided in the` lower face of the piston 31surrounding the stem 4| for engaging the annular rib seat in sealingrelation upon downward movement of the piston 31.

Formed in the wall between the two bores 36 and 44 is a chamber 55 intowhich the passage 42 opens. Chamber 55 is constantly open to atmospherethrough an exhaust passage and port 56.

With the piston valve 43 in its raised position seated on the annularrib seat 48, the piston Valve is above two ports 58 and 59 opening intothe bore 44 at substantially the same distance from the cover plate 46.Port 58 is connected through a pipe 6| to the control pipe I4.

Connecting the ports 58 and 59 in by-passing relation to the bore 44 isa passage 62 formed in casing 35 and containing a restricted portion orchoke 63.

With the piston valve 43 in its raised position, fluid under pressuremay be accordingly supplied at a rapid rate from the supply pipe I4through the branch pipe 6| and port 58 into the bore 44 and .out of thebore through port 59.

Upon the supply of uid under pressure to the chamber above the piston 31in a manner presently to be described, piston 31 is shifted downwardlyinto seated relation on the annular rib seat 5|, in which position thepiston valve 43 laps or covers the ports 59 and 59, thus preventing thesupply of fluid under pressure from the control pipe |4 to the port 59except at a restricted rate through the by-pass communication 62.

The reapplication control valve mechanism I8 further comprises a magnetvalve and switch device 65, which includes a suitable solenoid or magnetwinding 66. The magnet winding 66 is adapted to operate a pair ofoppositely seating valves 61 and 69 of the poppet type and a pair ofinsulated contact members 69 and 10 respectively.

The poppet valve 68 is attached to or formed integrally with a piston 12that operatesY in a bore 13 in the casing 35. Interposed between thecover plate 46, which covers the open end of the bore 13, and the lowerface of the piston 12 is a coil spring 14 which urges the piston 'I2upwardly to maintain the valve 68 seated on its associated valve seatwhen the magnet winding 66 is deenergized. The fiuted stems of thevalves 61 and 88 are of such length that when the valve 68 is seated,the valve 51 is unseated upwardly from its associated valve seat toestablish communication between a chamber 15 in which it is containedand a chamber 16 located between the chamber 15 and the bore 13. Port 59is constantly connected through a passage 'I8 with the chamber 'I5 and apipe 19 connected to the chamber 16 leads to the differential relayvalve mechanism |9. Accordingly, when the magnet winding 66 isdeenergized and the valves 61 and 99 are in unseated and seatedpositions respectively as shown,

`fluid under pressure may be supplied from the control pipe I4 throughthe branch pipe 9|, port 58, bore 44, port 59, passage 18, chambers 15and 16, and through the pipe 19 to the dierential relay valve mechanism|9.

With the valve 69 seated, the piston 12 is above an exhaust port 8| inthe wall of the casing 35 so that the chamber formed in the bore 13below the'piston 12 is thus vented to atmosphere. At the same time, afeed groove 82 around the piston establishes communication between thechamber at the upper side of the piston 12 and the chan ber at the lowerside of the piston.

In the raised position of the piston 12, it is also above the opening ofa passage 84 into the bore 13, the opposite end of which passage opensinto the chamber formed above the piston 31. 'Ihe opening of the passage84 into the chamber above the piston 31 comprises a restricted port 85and a relatively unrestricted passage in parallel relation therewith,the latter passage including a one-way valve of the ball type 86 whichis arranged to permit the supply of fluid under pressure through thepassage 94 into the chamber above the piston 31 and to prevent reverseflow of fluid under pressure therepast.

The switch contacts 69 and 19 of the magnet valve and switch device 65are carried on a sternk 88 moved by and in correspondence with themovement of the plunger actuated in response to energization anddeenergization of the magnet winding 66. Associated with the contact 69are a pair of spaced insulated contact fingers 89 and associated withthe contact 10 are a pair of spaced insulated contact fingers 99. Whenthe magnet winding 66 is deenergized, the stem 83 is raised to aposition such that the contacts 69 and 10 are shifted out of engagementwith the associated pairs of contact fingers.

When the magnet winding 66 is energized, the stem 88 is shifteddownwardly and the contacts 69 and 18 correspondingly moved intobridging engagement with the associated pairs of contact fingers. At thesame time, the valves 61 and 68 are shifted downwardly to seated andunseated positions respectively.

The manner in which the reapplication control valve mechanism |8functions will be hereinafter described in detail in connection with anassumed operation.

The differential relay valve mechanism |9 is of the type described indetail in Patent 2,191,822 of Clyde C. Farmer and will here be butbriefly described since reference may be had to this patent for adetailed description.

Briefly, the diierential relay valve mechanism I9 comprises aself-lapping relay valve mechanism including a supply valve 9|, arelease valve 92, and an operating plunger 93 having pivoted thereon afloating lever 94 for operating the valves 9| and 92.

Supply valve 9| controls communication between a branch pipe |5a of thesupply pipe |5 anda chamber 95 in the relay valve mechanism hereinaftercalled the pressure chamber, to which the brake cylinder I2 isconstantly connected as by a pipe 90. The release valve 92 controlscommunication between the pressure chamber 95 and atmosphere through anexhaust port 96.

The relay valve mechanism further comprises a pair of imperforateunconnected flexible diaphragms,` of different effective pressure areas,hereinafter respectively referred to as the larger diaphragm 91 and thesmaller diaphragm 96. As will be explained hereinafter, the diaphragms91 and 98 may be selected so as to have any desired ratio between theeffective pressure areas thereof.

The diaphragms 91 and 98 are secured in peripherally clamped relation inthe casing of the relay valve mechanism in coaxial spaced relation toeach other at one end of the plunger 93.

The larger diaphragm 91 has formed on the left-hand side thereof achamber 99 into which the pressure chamber 95 opens. A follower ||l|suitably guided in the casing and preferably attached to the flexiblediaphragm 91 engages the rounded end of the plunger 93 which projectsout of the pressure chamber 95 into chamber 99.

Formed between the two diaphragms 91 and 98 is a chamber |02. Suitablyadhering to the faces of the diaphragms 91 and 98 withinv the chamber|02 are followers |03 and |04 respectively which serve to maintain aminimum spacing between the diaphragms.

Formed at the' outer face, that is the righthand face, of the smallerdiaphragm` 98 is a chamber |05 with which the pipe 19 leading from thereapplication control valve mechanism I8 is in constant communication.through apassage 19a.

The differential relay valvev mechanism Vfurther comprises a magnetvalve |01 for alternatively connecting the chamber |02 between thediaphragms 91 and 98 to the passage 19a or to atmosphere.

Magnet valve |01 comprises a double beat valve |08 which is urged to anupper seated position by a coil spring |09 and actuatedto a lower seatedposition in response to energization of a magnet winding H0. In itsupper seated position, the valve |98 establishes communication from thepassage 19a to a passage III leading to and opening into the chamber |02between the diaphragms 91 and 98.

In its lower seated position, the communication between the passage 19aand the chamber I 02 is closed and communication established from thepassage III to a chamber II2 which is constantly open to atmospherethrough a large port IIS.

When the magnet valve |81 is deenergized and uid under pressure issupplied through the pipe 19 to the chambers |02 and |05, the fluidpressure forces on the smaller diaphragm 98 are balanced and only theunbalanced fluid pressure force on the diaphragm 91 is effective toshift the plunger 93 in the left-hand direction to effect seating of therelease valve 92 and unseating of the supply valve 9| in succession.Fluid under pressure is accordingly supplied from the supply pipe I5 tothe pressure chamber 95 and thence to the brake cylinder I2 through pipe99.

When the fluid pressure force in the pressure chamber 95 acting on theleft face of the larger diaphragm 91 becomes substantially equal to thefluid pressure force in the chamber |02, a spring II5 restores theplunger 93 in the right-hand direction sufficiently to reseat the supplyvalve l 9| but not to unseat the release valve 92. Fluid under pressureis accordingly maintained in the brake cylinder I 2 at a pressurecorresponding to the pressure established in the chamber I 02.

With the magnet winding I|0 of the magnet valve |01 energized and thevalve |08 correspondingly shifted to its lower seated position, fluidunder pressure is exhausted from the chamber |82 between the twodiaphragms 91 and 98 through port II3 and consequently the fluid underpressure supplied through the pipe 19 charges only the chamber |05 atthe outer face of the smaller diaphragm 98. In such case, therefore,only the unbalanced force of iluid pressure acting on the smallerdiaphragm 98V is eiective to shift the plunger 93 in theV lefthanddirection to effect successive seating and unseating of the release andsupply valves 92 and 9 I. Due to the larger area of the diaphragm 91 incomparison with the area of the diaphragm 98, the fluid pressureestablished in the pressure chamber 95 is effective at a lower valuethan previously to effect the reseating of the supply valve 9|.

Assumingthat the larger diaphragm 91 hasan eiective pressure area of tensquare units and the smaller diaphragm 98 has an effective pressure areaof eight square units, it will be seen that the pressure established inthe pressure chamber will bear the same ratio to the pressureestablished in the chamber |95 as the area of the smaller diaphragmbears to the area of the larger diaphragm 91. Thus, the pressureestablished inthe pressure chamber 95 will be eighty per cent of thatestablished in the chamber |05.

The sanding magnet valve 21 has a double beat valve similar to themagnet valve |01 on 'the differential relay valve mechanism and diil'erstherefrom in having a movable switch contact II8 which is shifted intocontact with a pair of insulated xed contacts I I9 in response toenergization of the magnet winding I2I thereof and restored to aposition out of engagement with the contacts II9, as shown, in responseto deenergization of the magnet winding I2I.

With the magnet winding I2| of the sanding magnet valve deenergized asshown, communication is established past the double beat valve thereoffrom a branch pipe |511 of the supply pipe to a pipe |23 having twobranches, one of which leads to the sanding reservoir 25 and the otherof which leads to the pressure switch 28, Accordingly, when the magnetwinding I 2| of the sanding magnet valve 21 is deenergized, the sandingreservoir 25 is charged to the pressure in the supply pipe I5 and thepressure switch 28 is actuated to its open position.

When the magnet Winding I2I of the sanding magnet .valve 21 isenergized, the double beat valve thereof is shifted to cut-01T thecharging communication for the sanding reservoir 26 and establish acommunication through which uid under pressure is supplied from thesanding reservoir 26 to a pipe |25 having two branches, one of whichleads to the sander 25 for one wheel unit and the other of which leadsto the sander 25 for the other Wheel unit.

Accordingly, as long as the magnet winding I2I of the sanding magnetvalve 21 is energized, uid under pressure continues to be supplied fromthe sanding reservoir 2E to the Sanders 25 to cause sanding of the railsuntil, of course, the supply of fluid in the sanding reservoir isexhausted.

The capacity or volume of the sanding reservoir 28 is so designed thatthe pressure therein reduces below five pounds per square inch in apredetermined time, such as thirty seconds.

,f Thus, notwithstanding the fact that the magnet winding -I2I of thesanding magnet valve 21 remains energized, sanding of the railscontinues only for a predetermined time.

Switch contacts II8 and II 9 magnet valve, winding I2I is energized toestablish a self-holding circuit for maintaining the magnet winding I2Ithereafter energized as long as the pressure switch 2| remains in closedposition. This operation will be hereinafter described in greater detailin connection with an assumed operation.

of the sanding Operation of equipment Let it be assumed that the car ortrain having the equipment shown in the drawing is traveling alongv theroad under power or coasting with the brakes released, that is, with thebrake valve handle I1a in its brake release position as shown. Let italso be assumed that the reservoir I8 is charged to the normal pressure,such as one hun- 21 are effective, once the magnet` valve mechanism dredpounds per square inch, from a fluid compressor not shown, and that thesupply pipe i5 and sanding reservoir 20 are correspondingly charged withfluid under pressure. The 'pressure switch 2| is in its open positionbecause the pressure in the control pipe I is at atmospheric pressureand the pressure switch 28 is in open position because of the fact thatthe sanding reservoir 26 is fully charged.

' The reapplication control valve mechanism I8 and the differentialrelay valve mechanism le are conditioned as shown in the drawing forreasons which will be made apparent hereinafter and the brake cylinderI2 is connected to atmosphere past the unseated release valve 92 of thedifferential relay Valve mechanism.

Let it now be further assumed that the operator desires to effect anapplication of the brakes in order to bring the car or train to a stop.To do so, he rst shuts off the propulsion power, if the power is on andthen shifts the brake valve handle I1a into its application zone anamount corresponding to the desired degree of application of the brakes.The control pipe I4 is thus charged to a corresponding pressure such asforty pounds per square inch. Pressure switch 2| is thus snapped to itsclosed position whenever the pressure in the control pipe I4 increasesabove ve pounds per square inch. At the same time fluid under pressureis supplied from the supply pipe I4 through the branch pipe 0I and at arapid rate through the port S8, bore lill, port 59, passage 18, past theunseated valve 01, chamber 16, pipe 19 and passage 19a to the chamber|05 at the outer face of the smaller diaphragm 90 of the relay Valvemechanism I9. At the same time, due to the fact that the magnet windingl of the magnet valve device |01 is deenergized for reasons hereinaftermade apparent, uid under pressure is also supplied from the passage 19ato the passage III and thus to the chamber |02 between the diaphragms 01and 98.

The relay valve mechanism I9 is accordingly l operated to supply fluidunder pressure from the supply pipe I5 to the pressure chamber 95 1andconnected brake cylinder I2. The pressure established in the brakecylinder I2 will be substantially equal to the pressure established inthe control pipe I4 due to the fact that the larger diaphragm 91 iselective to operate the relay I9. Thus, assuming forty pounds per squareinch pressure to be established in the control pipe, uid at a pressureof substantially forty pounds per square inch will be established in thebrake cylinder I2 to effect application of the brakes on the wheels |Iat the corresponding degree.

As long as the wheels II do not slip due to the application of thebrakes, the degree of application of the brakes remains as determined bythe pressure established in the brake cylinder I2, affected only byvariation of the coefficient of friction between the brake shoes and thewheels in well known manner.

As the car or train reduces in speed, the operator may in customarymanner eiect a reduction in the degree of application of the brakes inorder to prevent the sliding of the wheels as the car approaches a stop.Thus, if the operator shifts the brake valve handle Ila ,back towardbrake release position, the pressure in the con-v trol pip-e Ill iscorrespondingly reduced. The pressure in the chambers |02 and |05 of therelay valve mechanism I9 is thus likewise reduced by the back-now of uidunder pressuretherefrom to the control pipe I4 through the chargingcommunication previously described. Due to the reduction of the pressurein the chamber |02, the higher force of the pressure in the pressurechamber 95 overcomes the uid pressure force in the chamber |02 and thespring I|5 is accordingly eiective to shift the plunger 93 in theright-hand direction to effect the unseating of the release valve 92.The pressure in the pressure chamber 95 and in the brake cylinder I2 isaccordingly reduced by the exhaust through the port SB until such timeas the pressure in the brake cylinder and chamber 95 reducessubstantially to the pressure in the chamber |02, at which time thefluid pressure in the chamber |02 again becomes effective to shift theplunger 93 suiciently in the left-hand direction to reseat the releasevalve 92 and cut-off the further exhaust of uid under pressure from thebrake cylinder and chamber 95. Thus, the pressure in the brake cylinderI2 is correspondingly reduced as the pressure in the control pipe I isreduced.

When the car comes to a stop and the operator desires to effect therelease of the brakes before again starting the car or train, heA merelyrestores the brake valve handle Ila to its brake release position, thusreducing the pressure in the control pipe Ill to atmospheric pressureand correspondingly reducing the pressure in the brake cylinder I2 toatmospheric pressure.

Let it now be assumed that during an application of the brakes, eitherone or both of the wheel units |I begins to slip. In such case, one orboth of the wheel-slip-responsive devices 3| are effective to establisha circuit for energizing the magnet winding 6610i the magnet valve 65 ofthe reapplication control valve mechanism I8.

This circuit extends from the positive terminal of a suitable source ofdirect-current, sucnas the storage battery I3|, by way of a wire |32including the switch contacts 22 and 23 of the pressure switch 2|, abranch wire |33, one or both of the switch devices 3Ia of thewheel-slip-responsive devices 3| which are in parallel relation, to awire |34, thence through a branch wire |35 including the magnet winding66 of the magnet valve 65 to the opposite or negative terminal of thebattery I3| as through a ground connection in the manner shown.

Upon the energization of the magnet winding 66 of the magnet valve 65,the movable contacts 63 and 10 are shiftedinto engagement with theirrespective pairs of contact lingers.

The contact 69 is effective when engaging its associated contact ngers89 to establish a circuit for energizing the magnet winding I0 of themagnet valve |01 of the differential relay valve mechanism I9 and themagnet winding of the relay 29. At the same time, the contact 10 iseffective while engaging its associated contact lingers 90 to establisha circuit for energizing a sanding train wire |31 which extendsthroughout all cars of the train. Energization of the sanding wire |31is effective to cause energization of the magnet winding |2I of thesanding magnet valve 21 for the respective wheel trucks on all cars ofthe train in manner hereafter described.

The circuit for energizing the magnet winding I I0 of the magnet valve|01 and magnet winding of the relay 29 extends from the positiveterminal of the battery I3| by way of the wire I32fincluding the closedpressure switch 2 I, contact ngers 89 and contact 69 of the magnet valve65, a wire |39, and thence in parallel through the magnet winding ||0 ofthe magnet Valve |01 and the magnet winding ol the magnet valvel |01andthe magnet winding of the relay 29 to the negativeV terminal of thebattery |3|, as through ground connections inthe manner shown. Thecontact of the relay 29 is accordingly actuated to its picked-up orclosed positionbut, due to the fact that the pressure switch 28 is inopen posi-A tion at this time, no immediate `eiect results from itsoperation.

The energization of the magnet winding ||0 of the magnet valve |01 iseffective to cause an immediate'and rapid reduction of the pressure inthe chamber v|02 dueto the exhaust of fluid under pressure therefromthrough the exhaust" port ||3 of the magnet va1ve|01. Y

Thus, the instant that either of the wheel units begins to slip, thepressure in the brake cylinder I2 is instantly reduced at a rapid rate.The circuit 'for energizing the magnet winding |2| of the sanding magnetvvalve 21 extends from the IJQSitive terminal ofthe battery |3| by wayof the wire |32 including theV closed pressure switch 2|, contactingersA 90 and contact 10- of the magnet valve` 65, a wire |4|, to thesanding wire |31 and thence in parallel through the mag net winding |2|of each sanding magnet valve on the car or train to the oppositeterminal of the battery |3l. In the drawing, the circuit ex.- tends fromtheysanding wire |31Vby way of a branch wire |152 including magnetwinding |2| to theV oppositeterminal of the battery 3|, as

through a ground connection shown.

Fluid under` pressure is accordingly supplied from the sanding reservoir26 ,to thesanders 25 to eifect sanding.k of the rails-in advance of thewheels throughout thc train.

Upon the energization of the magnet winding 66 of the magnet valve65 aspreviously described, the valves 61 and 68 are shifted to seated andunseated positions respectively. Thus, theV communication through whichfluid under pressure is supplied to the chambers |02 and |85 of thedierential relay valve mechanism I9 is closed by the seating of thevalve 61 and a communication is established by valve 68 through whichthe pressure in the chamber |05 is supplied back through the passage 18aand pipe 19 to the chamber above the piston 12. The feed groove 82 issufficiently small that the pressure supplied to the chamber above thepiston 124 overcomes the spring 14 and shifts the piston 12 downwardlypast the exhaust port 8| into engagement with a stop lug |44 formed onthe cover plate 46. Fluid under pressure is thus exhausted from thechamber |05 at a restricted rate throughvthe 1 port 8| and due tothe'restriction ofthe port 8|, a considerable quantity of theuiddischarged from the Achamber is supplied through the passage 84 pastthe one-way valve 86at a rapid rate to charge the chamber above thepiston 31. Piston 31 is thus instantly shifted downwardly into seatedposition on'the annular rib seat 5|, thus correspondingly shifting theypiston valve 43 into a position closing the opening of the ports 58 and59 into bore 44.

. Upon the equalization of the pressure in the chamber |05 of the relayvalve mechanism 9 and in the chamber above the piston 31, the continuedmaintenance of the piston 12 in engagement with the stop lug |44 resultsin the reduction of the pressure simultaneously in the chamber |05 andin the chamber above the piston 31. The pressure in the chamber |05 willhowever reduce at a relatively rapid rate through the port 8| 'whereasthe pressure in the chamber above the piston 31 will reduce at arelatively slow rate through the restricted port 85 and passage 84 sincethe ball valve 88 reseats to prevent the return of fluid under pressuretherepast. Accordingly, until such time -as the pressure in the chamberabove the piston 31 reduces to a value such that the spring 41 canrestore the piston 31 upwardly, the piston valve 43 remains in positionblocking the ports 58 and 59.

The size of the port 85 relative to the volume of the chamber above thepiston 31 is such as to cause the piston to be maintained seated on therib seat 5| for a predetermined time sufficiently long for the car ortrain to come to a stopin a, response to the application of the brakes.

It will thus be seenthat due to the reduction of the pressure in thechamber |02 in response to the energization of the magnet winding ||0 ofthe magnet valve |1 and also to the reduction of the pressure in thechamber |05 in response to speed corresponding to vehicle speed withoutac- 1 tually sliding.

When the wheels cease to accelerate back to a speed corresponding tovehicle speed, while slipping, at a rate exceeding ten miles per hourper second and. sufficient to maintain the switches 3|a of thewheel-slip-responsive devices in closed position, the switches 3|a openand thus interrupt the circuit for energizing the magnet winding 66- ofthe magnet valve 65. If the pressure above thepiston 12 has alreadyreduced sufl'iciently at such time, the spring 14 acts to shift thevalves `61 and 68 upwardly again to unseated and seated positions. If,however, a sumcient pressure remains in the chamber above the piston 12to maintain the piston 12 downwardly, then the valves 61 and 68 are notrestored to their unseated and seated positions until the piston 12 isrestored upwardly by the spring 14.

When the piston 12 passes above the exhaust port 8|, dash-pot action ofthe piston 12 in the bore 13 is prevented due to the feed groove 82equalizing the pressure on opposite sides of the piston. Thus, seatingof the valve 68 by the piston 12 is not prevented or delayed.

With piston 12 in its raised position seating valve 68, iluid underpressure continues to be exhausted ata restricted rate from the chamberabove the piston 31 through the passage 84 and the port 8|. v

Upon the deenergization of the magnet winding 66 of the magnet valve 65,the `contacts 69 and 10 are shifted upwardly out of engagement withtheir respective associated pairs of contact iingers.89 and 90.

In view of the fact that the Slipping wheels will be restored'to aspeedcorresponding to vehicle speed in a time not exceeding severalseconds, the pressure switch 2B associated with the sanding reservoir 26is still in open position. Consequently the separation of the contact 60from the contact-lingers 89 effects deenergization of the magnet winding||0 of the magnet valve |01 and of the magnet winding of the relay 29which correspondingly drops out.

The separation of the contact 10 from its associated contact fingers 90interrupts the circuit for energizing the sanding wire |31. However, themagnet winding |2| of the sanding magnet valve 21 remains energized dueto the self-holding circuit established therefor by the engagement ofthe .contacts II8 and H9 thereof when the magnet winding I2I was firstenergized. This holding circuit extends from the positive terminal ofthe battery I3I on the corresponding car through the wire I32 includingthe closed pressure switch I2I, a branch wire ll including the contactfingers IIS and movable Contact IIS of the sanding magnet valve 27, andwire |22 including the magnet winding I2I to the negative terminal ofthe battery I3I through the ground connection shown.

It will thus be apparent that once the magnet winding I2I of eachsanding magnet valve 2l is energized in response to the initial slippingof the wheels on any car of the train, sanding of the rails is continuedthereafter on all cars independently of the restoration of the slippingWheels to a speed corresponding to vehicle speed.v

With the valve 6l of the magnet valve 65 restored to its unseatedposition and the magnet winding IIB of the magnet valve |07 of thedifferential relay valve mechanism I9 deenergized, uid under pressure isagain resupplied to the chambers I92 and |95 of the relay valvemechanism I9 from the control pipe I4. In this case, however, due to thefact that the piston valve 23 blocks the ports 58 and 59, fluid underpressure is supplied from the branch pipe 9| of the control pipe il onlythrough the by-pass communication 52 including the choke 53. Thus, thepressure of the fluid is restored in the chambers I S2 and I at arelatively slow or restricted rate in comparison to the normal rate.

It will accordingly be seen that the relay valve I mechanism I9 operatesto restore the pressure in the brake cylinder I2 and thus reapply thebrakes on the slipping wheels at a gradual or slow rate, thus minimizingthe possibility of recurrence of wheel slipping. The pressure restoredin the brake cylinder associated with the slipping wheels will, however,ultimately attain a value substantially equal to that established in thecontrol pipe I4.

If a slipping of the same wheel unit or units I I again occurs duringthe same application of the brakes and before pressure switch 28 closes,the above operation is repeated and fluid under pressure is againrapidly released from the brake cylinder I 2, and then restored at arestricted rate.

If wheel-slip re-occurs at a time subsequent to the blow-down of thepressure in the sanding reservoir sufficiently to close the pressureswitch 28, a different operation occurs which will now be described.With the pressure switch 28 in closed position, the' energization of themagnet winding 69 or" the magnet valve 55 in response to the slipping ofthe wheels initially completes the circuit for energizing the magnetwinding III] of the magnet valves I Ill and |07 and the magnet windingof the relay 29 as previously described. Upon the pick-up of the relay29, however, a holding circuit is established independently of themagnet valve Vswitch contacts 65 for maintaining the relay 29 picked upand the magnet winding H of the magnet valve IU'I energized.

This circuit extends from the positive terminal of the battery I3! onthe corresponding car by way of the wire I32 including the closedpressure switch 2l, a branch wire |53 including the contacts 22 and 23of the pressure switch 28 and the contact of the relay 29 to wire |39,then in parallel through the magnet Winding IIU of the magnet valveIIJ'I and the magnet winding of the relay 29 to the negative terminal ofthe battery ISI through the ground connection shown.

It will thus be apparent that upon the elapse of a predetermined time,which is illustratively shown as the blow-down' time of the sandingreservoir 26, the restoration of the slipping wheels to a speedcorresponding to vehicle speed and the consequent deenergization of themagnet winding 66 of the magnet valve 5 does not result inthedeenergization of the magnet winding III) of the magnet valve IUTbecause of the holding circuit therefor just described.

Accordingly, when fluid under pressure is resupplied to' the relay valvemechanism I9 through the by-pass communication including the choke 63,the chamber |62 remains connected to atmosphere and fluidunder pressureis resupplied only to the chamber 195. Thus, the reapplication of thebrakes on the Wheels which slipped following restoration thereof tovehicle speed will occur at a restricted or slow rate as in the previousinstances but the ultimate value to which the pressure in the brakecylinder I2 is restored will be less than the pressure established inthe control pipe I4. In the case of diaphragms 97 and 98 having an arearatio of ten to eight, as assumed, the ultimate pressure restored in thebrake cylinder I2 will be eighty per cent of that remaining establishediin the control pipe l. Thus, if the pressure in the control pipe I4 isforty pounds per square inch, the pressure ultimately restored in thebrake cylinder I2 will be thirty-two pounds per square inch.

Due to the increase in the adhesion or rolling friction between thewheels and the rails caused by sanding of the rails, it is unlikely thatwheelslip will reoccur during the sanding period. If wheel-slip occursafter sanding has ceased, it is essential that the degree of applicationof the brakes restored on the slipping wheels be limited to a valuewhich is less than that which initiated the slipping. It will thus beseen that by permitting the restoration of the pressure in the brakecylinders following wheel-slip to a value which corresponds to thatestablished in the control pipe I4 at the time wheel-slip began, as longas san-ding operation continues, a shorter stopping distance may beobtained than if the pressure restored in the brake cylinder werelimited immediately following the rst slipping of the wheels to a lowervalue than that established in the control pipe. Moreover, thelimitation of the pressure restored in the brake cylinders to a valueless than that which initiated the wheel-slipping only after theexpiration of the sanding period prevents recurrence of slipping cyclesafter the expiration of the sanding period.

When a car or train comes to a stop following an application of thebrakes during which the wheels slipped in the manner previouslydescribed, the brakes remain applied to a degree determined by thepressure in the brake cylinder I2 which may be equivalent to or afraction of the pressure in the control pipe I :l depending upon whethermagnet winding I ill of the magnet valve lill remains energized or isdeenergized.

To release the brakes before again starting the car, the operator merelyrestores the valve handle Ila to its brake release position aspreviously described. Ordinarily, the pressure in the chamber above thepiston 3l will have blown-down sufficiently before it is again desiredto start the car or train that the piston valve i3 will have beenrestored upwardly into seated relation on the rib seat 48, thus openingthe ports 58 and 59. Thus,

upon the restoration of the brake valve handle I'Ia to its brake releaseposition, uid under pressure will be released from one or both of thechambers and ID2 of the relay valve mechanism I9 at a rapid rate and therelay yValve mechanism I9 will operate correspondingly to vent fluidunder pressure from the brake cylinder I2 at a rapid rate.

When the pressure switch 2| -opens in response to the reduction of thepressure in the control pipe I 4 below five pounds per square inch, theholding circuit for maintaining the magnet winding I2I of the sandingmagnetvalve on the corresponding car is interrupted as well as theholding circuit for the relay 29 and the magnet valve Iil'l if it isestablished. Upon the deenergization of the magnet winding vI2I vof thesanding magnet valve 2'I, communication is vrestoredithrough which thesanding reservoir26 is recharged to the pressure in the supply pipe I5and the pressure switch28 is restored to its open position.

Inadapting'myiinvention to a train brake system, it will be apparentthat the equipmentdescribed will be'substantially duplicated for eachwheel truck except that a single battery I3I` and a single pressureswitch 2| Vfor each car is all that is required. If it is desired toprovide only one battery I3I Aand pressure switch '2| for an entiretrain, then the wire |32 must be connected to an additional train wire,not shown in the drawing, to supply current frointhe 'single battery I3Ito all cars of the train under control of the 'single pressure switch2l. A

Accordingly, while I have shown only a simplied `embodiment of my.invention, various omissions, additions, or modifications in theequipment shown will be obvious to those skilled `in the art foradapting the system to operation in a train brake system, withoutdeparting fromthe spirit of my invention. It is accordingly not myintention to limit the scope ofv my invention except in accordance withthe terms of the append- .ed claims.

Having now described my invention, what I claim as new and desire tosecure by Letters Pat- .ent is:

1. Vehicle wheel brake control apparatus of the -type in which thebrakes associated with 'the -wheels. are applied and released under thecontrol .of the operator of the vehicle comprising, in comv bination,means responsive to the rotative decelerationof a wheel of the vehicleat a slipping rate caused by application of the brakes, means controlledby said wheel-'slip-responsive means and operative when the said wheelslips for efent degrees depending upon whether a certain uniform timehas or has `not elapsed following vthe instant the wheel rst beginsto-slip during .any one application of the brakes.

2. Vehicle wheel brake control apparatus of .the type in which thebrakes associated with the i .wheels are applied and released under thecon- 'trol of the operator of the vehicle comprising, in combination,means responsive to the rotative deceleration of a wheelof the vehicleata slipping irate `caused by application Yof the brakes, means Cilcontrolled by said wheel-slip-responsive means and operative when thesaid wheel-slips for effecting a rapid release of the brakes associatedwith said wheel so that the wheel ceases to decelerate and acceleratesback toward a speed corresponding to vehicle speed-without locking and-operative thereafter to cause reapplication of the brakes on `the saidwheel, and means effective if the reapplication of the brakes effectedby the last said means occurs within a certain uniform time followingthe instant the wheel first begins to slip during any one applicationfor permitting the `last said means to effect reapplication of thebrakes on the wheel to a degree substantially corresponding to that ineffect at the time the wheel begins to slip and operative to cause thelast said means to effect reapplication of the brakes onthe wheel to adegree less than that in eifect at the time slipping of the wheel beganif reapplication of the brakes occurs subsequent `to the elapse of saidcertain uniform time. f

3. In a' vehicle wheel brake control apparatus ofthe type having meansproviding a communication chargeable kwith fluid y*at differentpressures to correspondingly select the degree of application of thebrakes, a brakel cylinder for applying the brakes associated with avehicle wheel in accordance with'the pressure of uid supplied thereto,and a relay valve mechanism controlled according to the pressureestablished in the communication for supplying iiuid at a pressure whichmay bear selectively different ratios to the pressure established in thecommunication, the combination of means responsive to the rotativedeceleration of the vehicle wheel at a slipping rate, means controlledby the wheel-slip-responsive means and effective when the wheel beginsto slip for causing operation of the relay valve means to effect areduction of the pressure in the brake cylinder and thereafter theresupply of iiuid under pressure kfrom the communication to the relayvalve means to effect a resupply of fluid under pressure to the brakecylinder, and timing means set in Aoperation at the instant the Wheelrst'begins to slip during any one application for controlling the relayvalvemechanism to cause it to restore a pressure in thebrake cylinderwhich bears a certain one ratio to the pressure in the communicationonly if the relay valve means operates to resupply fluid under pressureto the brake 'cylinder at a time subsequent to the elapse of Va certainuniform time following the instant the wheel first begins to slip duringany one applicaton.

4. In a `vehicle wheel brake control apparatus of the type having acontrol pipe chargeable Awith fluid at different pressures to select thedegree vof application of the brakes, a brake cylinder effective tocause application of the brakes associated wtih a vehicle wheel inaccordance with the pressure of fluid supplied thereto, and-adifferential relay valve mechanism in- "cluding afmagnet valve device,the relay valve mechanism being controlled in accordance with thepressurein the control pipe to effect the supply of fluid at a pressuresubstantially equivalent to that in the control pipe or a certain fixedfraction of thepressure in the control pipe depending upon whether themagnet valve device thereof is deenergized or 4energized respectively,the combination of lmeans responsive to the rotative deceleration of thevehicle wheel at a slipping rate, valve means operatively controlled bythe wheel-slip-responsive rmeans and elective `when Vwheel at a slippingrate and effective upon -the the wheel slips for cutting off the ,supplyof fluid `under pressure from the control pipe to lthe relay valvemechanism and releasing fluid under pressure therefrom to effect a,corresponding release of fluid under pressure from the l brake cylinder,and timing means set in ,operation in response to the first operation ofthe wheel-slip-responsive means during any one application and effectivewhen the wheel slips again after the elapse of a certain uniform timeforeffecting continued energization of the magnet Avalve of the relay valvemechanism, whereby to cause the relay valve mechanism to selectivelyrestore pressure in the brake cylinder which is equal to the pressure inthe control pipe or a certain fixed fraction thereof depending uponwhether or not the certain uniform interval of time has not or haselapsed respectively.

5. In a vehicle wheel brake control apparatus of the type having a brakecylinder to which fluid under pressure is supplied to effect applicationof the brakes associated with a Vehicle wheel and from which fluid underpressure is released to effect release of the brakes, the combination ofa control pipe chargeable with fluid at different pressures, a relayvalve mechanism variously conditionable to cause fluid at a pressurecorresponding substantially to that established in the control pipe tobe supplied to the brake cylinder or fluid at a pressure which is acertain fixed fraction of that in the control pipe depending upon thecondition thereof, means effective upon the slipping of the vehiclewheel for effecting the release of fluid under pressure from the relayvalve mechanism and the consequent release of fluid under pressure fromthe brake cylinder and thereafter effective to cause resupply of fluidunder pressure to the relay valve mechanism and the consequent resupplyof fluid under pressure to the brake cylinder, and timing means eectiveonly after a certain uniform time following the instant the wheel rstbegins to slip during any one application for varying the condition ofthe relay valve mechanism to cause it to resupply uid under pressure tothe brake cylinder at a pressure which is the said certain fixedfraction of the pressure in the control pipe.

6. In a vehicle wheel brake control apparatus of the type having a brakecylinder to which fluid under pressure is supplied to effect applicationof the brakes associated with a vehicle wheel and from which fluid underpressure is released to effect release of the brakes, the combination ofa control pipe chargeable with fluid at different pressurescorresponding to the desired degree of application of the brakes, arelay valve mechanism controlled according to the pressure in the saidcontrol pipe, the relay valve mechanism having electroresponsive meansand operative to supply fluid at a pressure substantially equal to thatin the control pipe when the electroresponsive means is deenergized Iandat a pressure which is a certain fraction of that in the control pipewhen the electroresponsive means is energized, means effective inresponse to the rotative deceleration of the vehicle wheel at a slippingrate for effecting the release of fluid under pressure from the lrelayvalve mechanism and the consequent release of fluid under pressure fromthe brake cylinder and thereafter operative to cause the resupply offluid under pressure to the relay valve mechanism and the consequentresupply of fluid under pressure to the brake cylinder, and timing meansset in operation in response to the rotative deceleration of the vehicleelapse of a certain uniform time `and whenever ,slipping of the wheelagain occurs for effecting substantially equal to or a certain fractionof the pressure in the control pipe depending upon whether said certainuniform time has not or has elapsed respectively.

7. Vehicle Wheel brake control apparatus cornprising, in combination, acontrol pipe chargeable with fluid at different pressures in accordancewith a desired degree of application of the brakes, relay valvemechanism variously conditionable and operative in response to thepressure established in said control pipe to cause fluid to be suppliedto effect application of the brakes at a pressure having differentratios to the pressure in the control pipe depending upon the conditionof the relay valve mechanism, a reservoir normally charged with fluid inexcess of a certain pressure, pressure responsive means operativelyresponsive to the reduction of the pressure in said reservoir below saidcertain pressure, means operatively responsive to the deceleration of avehicle wheel at a slipping rate, means controlled by thewheel-slip-responsive means and effective when a Wheel slips for causingoperation of the relay valve mechanism to release fluid under pressurefor releasing the brakes and effective also to initiate a continuedreduction of the pressure in said reservoir, said last means beingfurther effective as the slipping wheel returns back toward a speedcorresponding to vehicle speed for causing operation of the relay valvemechanism to resupply uid under pressure to reapply the brakes andeffective jointly with .the said pressure responsive means only afterthe pressure of said reservoir reduces below said certain pressure forcausing the relay valve means to be conditioned to resupply fluid underpressure at one certain one of said ratios with respect to the pressurein the control pipe.

8. Vehicle wheel brake control apparatus comprising, in combination,variously conditionable relay valve means operative when in onecondition thereof in response to a given operating pressure to supplyfluid at a certain pressure for effecting application of the brakesassociated with the vehicle wheels and when in a different conditionthereof to supply fluid at a lower pressure to effect application of thebrakes in response to the given operating pressure, a reservoir normallycharged with fluid under pressure, means operative upon the rotativedeceleration of a vehicle wheel at a slipping rate for effectingoperation of the relay valve means to release uid under pressure torelease the brakes and at the same time effective to initiate acontinued reduction .of the pressure in said reservoir, said last meansbeing effective to cause operation of the relay valve means to resupplyfluid under pressure to effect reapplication of the ybrakes as theslipping wheel returns back toward its speed corresponding to vehiclespeed, and means effective when a Wheel slips following the reduction ofthe pressure in said reservoir below a certain uniform pressure forconditioning the relay valve means Ato resupply fluid to effectapplication of the brakes at the said lower pressure.

9. In a vehicle wheel brake control apparatus llthetype having abrake'cylinder to "Whi'c/h'l underp'ressure is supplied to eiectapplication of the brakes 'associated withone or more vehicler cylinderat a pressure having one certain xie'd ratio to the operating pressureWhen in one iconldition 'and at a pressure having a, certain "iixedlower ratio to the operating pressure when in a different condition,means operatively responsive 'tothe rotative deceleration of one of saidWheels jat a slipping rate, a reservoir normally` charged with 'uidunder pressure, 'pressure responsive 'nieans controlled according to thepressure in said reservoir, and means controlled bythe Wheelafz'iaaosempresaria-mars fand foam-'ive rifers "wired-slips tb feirect operationfor rherlay valve fag@ relay valve Mechanism u) freeway ma 15 mechanism*to respply uia under pressure fro

